There's a cha program over here called QQ and it's hugely popular. You even see QQ addresses on business cards
Typing characters is difficult on a keyboard as there are far too many for each to have a key. About 4000 for a basic vocabulary and 10 times that for the educated wordsmith. There are two solutions:
The first relies on the latinised version of Mandarin Chinese called pinyin. This can then be typed in using the regular keys. A list of possible characters comes up and the right one selected by the cursor or by choosing the appropriate number. Since no special equipment is required this is the preferred option in many cases.
Characters are composed of just a limited number of brush-strokes and must be written in a very strict order. That means that the second method, a kind of predictive text, can home in on the correct character very quickly when brush-strokes are entered with a stylus or adapted keyboard.
Displaying characters is no big issue. HTML coding now allows for pretty much every writing system to be displayed, so long as this is noted in the section.
One complication stems from the fact that, on the mainland, Chinese characters were simplified by the Communists in a bid to increase literacy. Many overseas Chinese refused to adopt this system - and so there are both simplified and original characters out there.